What Mini codes (P0304, P0128, P0011, P0016, P0420, P0171) actually mean on Mini engines — the real cause, the common misdiagnosis, and the honest UK repair cost.
These are the OBD fault codes we see most often on Mini vehicles in the workshop, with the real cause on Mini engines rather than the generic textbook definition, plus the honest independent-garage cost.
Mini fault codes explained
- P0304 — Cylinder 4 misfire on Mini — N14/N18 Prince engine coil/plug failure plus timing chain stretch causing cyl 4 misfire on high-mileage Cooper S. Typical UK cost £140–£1800.
- P0128 — Coolant below thermostat on Mini — the electric thermostat housing on N14/N18 Prince engines is a known failure. Typical UK cost £180–£420.
- P0011 — Intake camshaft over-advanced on Mini Cooper S — the Prince N14/N18 VANOS solenoid and stretched timing chain are the usual suspects. Typical UK cost £220–£1800.
- P0016 — Crank/cam correlation on Mini Cooper S — Prince N14/N18 timing chain stretch is one of the best-known faults in the trade. Typical UK cost £900–£1900.
- P0420 — Catalyst efficiency below threshold on Mini Cooper / Cooper S — typically a knackered cat after years of oil-burning Prince engines. Typical UK cost £250–£1400.
- P0171 — System too lean on Mini — Prince N14/N18 PCV diaphragm and intake gaskets are the classic causes. Typical UK cost £240–£650.
- P0017 — Crank to exhaust cam correlation on Mini — Prince timing chain has stretched, partner code to P0016. Typical UK cost £900–£1900.
- P0014 — Exhaust cam over-advanced on Mini Cooper S — Prince VANOS solenoid sludging or chain stretch. Typical UK cost £180–£1900.
- P0299 — Turbo underboost on Mini Cooper S — PCV diaphragm leak and charge pipe splits are the typical causes. Typical UK cost £180–£1400.
- P0507 — Idle speed higher than expected on Mini — N12/N14/N18 Prince engine vacuum leak from PCV. Typical UK cost £180–£580.
- P0341 — Camshaft position sensor performance on Mini — N12/N14/N18 Prince sensor and VVT solenoid overlap. Typical UK cost £100–£420.
Codes are generic across manufacturers, but the fix is not. The same code on a Mini usually points at a different component than it would on another make, which is why a make-specific diagnosis saves money before any parts are bought.